Phar::isCompressed

Description

This
method requires the php.ini setting phar.readonly to be
set to 0 in order to work for Phar
objects. Otherwise, a PharException will be thrown.

Returns Phar::GZ or PHAR::BZ2 if the entire phar archive is compressed
(.tar.gz/tar.bz and so on). Zip-based phar archives cannot be compressed as a
file, and so this method will always return FALSE if a zip-based phar archive is queried.